nope i came up with this name on my own and i only spell it seikay its the name ive used ofr a long time, so no im not. yes she wasnt a part but this game takes place between CoM and KH2 so she is already being held hostage.
She was a hostage from her "birth" to he end of CoM, she was a hostage. After that, Riku took her so she could restore Sora's memories, and let Axel go. She wasn't a prisoner in KH2. She told Sora she was going to restore his memories, regardless on whether she wanted to or not.